Demystifying fats and oils, part two

Why can only certain
fats be used in cooking, meaning heated to high temperatures?

Why should others
only be used unheated?

Our
main concern when it comes to consuming fats and oils is rancidity.
Some oils are more prone to rancidity than others. The deciding factor is the
chemical makeup of a particular oil or fat.

The building blocks of fats are called fatty acids. They
come in three forms: saturated, monounsaturated, and polyunsaturated.

The saturated fatty
acids are straight chains of carbon atoms with two hydrogen atoms attached
to each. Because of their straight shape, the chains pack together well and
form a semisolid consistency at room temperature. Butter, ghee (pure milk fat, also called clarified butter), lard (from
pork), tallow (from beef), coconut oil and palm oil consist predominantly of
saturated fatty acids. These are very stable and do not become rancid easily.
They can be heated to high temperatures without a compromise in quality. They
can be used for cooking, baking, sautéing, and with the exception of butter,
frying. Butter, because it is not pure fat, is not well suited for frying—its
lactose and protein particles tend to burn and turn black rapidly. Ghee, on the
other hand, because it is pure milk fat, does work well for frying. For the
same reason, ghee is suitable for those with lactose intolerance. But regular
butter is fine when heated in gentler ways. It is an especially good compliment
with steamed vegetables—add some at the end of the cooking process to ensure
absorption of fat-soluble vitamins and enhance taste.

The monounsaturated
fatty acids have one double bond between two carbon atoms, leaving the two
double-bonded atoms with only one hydrogen atom each and causing a bend in the
chain. Because of this bend, monounsaturated fatty acids do not pack together
as well as the saturated ones. They become liquid at room temperature and
remain solid only when refrigerated. Olive
oil is the most commonly used oil that consists of mainly monounsaturated fatty
acids, but almond, avocado, cashew, macadamia, peanut and canola (or rapeseed)
oils are monounsaturated as well. These fatty acids are fairly stable and
are therefore suited for cooking, baking and sautéing.

The polyunsaturated
fatty acids have two or more double bonds—two or more bends—which means
their molecular structure resembles that of a semicircle. They do not pack well
together at all and are therefore liquid even when refrigerated. Common oils with high polyunsaturated fatty
acid content are made from corn, flaxseeds, grape seeds, pumpkin seeds,
safflower seeds, soybeans, sunflower seeds, walnuts, wheat germ and sesame
seeds.

Rancidity
is the main problem with all polyunsaturated fatty acids.
Light, air, and heat affect their freshness and quality. Therefore, oils
containing predominantly polyunsaturated fatty acids should never be heated or
used in cooking. They can be used in cold dressings or sprinkled over cooked
food when served. They should always be kept in the refrigerator.

Polyunsaturated fatty acids fall into two main groups: omega
3 and omega 6. These names reflect the location of the first double-bond at
either the third or sixth position in the chain. Omega 3 is very reactive and
goes rancid particularly easily.

Omega 3 and 6 are called essential fatty acids because our
bodies cannot manufacture them and we need to get them from food. Most of the
polyunsaturated oils have larger amounts of omega 6 than omega 3. Flaxseed is
the exception, with a higher proportion of omega 3. When it comes to the
balance between omega 3 and omega 6, the best ratio for human consumption is
1:2. Too much omega 6 can lead to
inflammation and blood clotting. Omega 3, on the other hand, is
anti-inflammatory and blood-thinning. Because of the recent overemphasis on
polyunsaturated oils, many people are consuming too much omega 6 and are in
need of omega 3 to return to a place of balance—hence the popularity of
flaxseed oil and omega 3 fish oil.

Now
that you have an understanding as to which oils are predominantly saturated,
monounsaturated and polyunsaturated—and you can always check the proportion of
each by reading the package label—you know which oils are suitable for cooking
and which are to be used only cold: use
saturated oils and fats, such as ghee, lard, coconut oil and palm kernel oil for
cooking at high temperatures, use monounsaturated oils, such as olive oil,
almond oil and peanut oil for light cooking like sautéing and baking and use
polyunsaturated oils, such as pumpkin
seed oil, sunflower seed oil and walnut oil cold in
dressings or sprinkled over your cooked food as you serve it.